Method of tempering glass



Nov. 13, 1945.: G. WHITE v METHO OF TEMPERING GLASS Filed April 7, 1941v:inventor DE UMIDIFYE 65K/ew WHITE,

Bgv 8 Patented Nov. 13, 1945 Mnrnon F TEMPERING GLASS Gerald White,Toledo, Ohio, assgnor to Libbey'- Owens-Ford Glass Company, Toledo,Ohio,

corporation of Ohio Application April 7, 1941, serial No. 381,225 y 2claims. (cl. ia-89) The present invention relates to an improved methodof tempering glass..

In the usual method of'tempering glass, the glass is ilrs't heated in asuitable furnace yto a temperature approximating the softening point ofthe glass, after which it is withdrawn from the furnace and rapidlycooled by jets or blasts of air directed upon the glass surfaces underpressure.

The treatment of the glass in this manner produces a marked temperaturedifferential between the interior and the surface portions of the glass,with the result that the hot interior glass is prevented fromcontracting when it cools by the stiilening of the cooler surfaceportions whereby the outer surfaces of the glass are placed undercompression and the interior thereof under tension. 'I'his strainedcondition of tempered glass materially increases its mechanical strengthand further modifies its breaking characteristics in that if and whenbroken it will disintegrate into innumerable small and relativelyharmless particles instead of breaking into large dangerous pieces orslivers as is the case with ordinary glass.

'I'he cooling means usually employed comprises a pair of spaced blowerheads between which the highly heated glass is received; each blowerhead being provided with a plurality of outlets through which jets orblasts of air are projected against .the glass surfaces. To effect amore even distribution of the air over the glass and in consequence amore uniform cooling thereof, it4 is desirable that relative movement.between the blower heads and glass be effected during the coolingoperation'.

-1 The effect of the cooling operation is to produce strain'in the glassat selected points whereby a 'predetermined desired breaking pattern maybe obtained.

The character or type of break obtained depends, among other factors,upon the time and temperature cycle followed in the temperingoperations, and in order to set up the desired strain in the. glasswhereby to produce this predetermined breaking pattern. it is essentialthat the glass be heated 'for a predetermined length of` time to a..predetermined temperature and then cooled: for a predetermined lengthof time at a predetermined temperature. Any variation in the time andtemperatln-e cycle after it has once been established to obtain adesired type of break will ailect or modify the breaking pattern of theglass or, in other words, the character of its burst.

Beretofore, it has been customary for the sup- Ply .of cooling air forthe blower heads to be taken directly from the atmosphere and withoutblower heads and projected thereby upon the glass; Due to variations inatmospheric temperature, however, the temperature of the outside airsupplied to the blower heads will vary greatly from day to day andlikewise the humidity or moisture content ofthe air will vary. Thiscontinual varying of the temperature and humidity of the cooling airrenders diiiicult the establishment and maintenance of predeterminedtemperature conditions over any considerable length of time, as a resultof which the breaking pattern of successive glass articles producedwill` tend to vary making difficult the manufacture of a constant,uniform product.

It is an aim of this invention to provide a nov method of temperingglass wherein a more positive and accurate control of the air supply forcooling is obtained by feeding conditioned air t0 the-blower heads tothe end that a more constant, uniform tempering of the glass can beachieved to produce a more uniform product having a predeterminedbreaking pattern.

Generally stated, this is achieved by conditioning the `air supply sothat it has a constant, predetermined temperature and moisture content.By maintaining the temperature and humidity of the cooling air constant,lit is possible to establish and maintain predetermined conditions as tocooling even though the atmospheric tempera'- ture may undergoconsiderable variation both as regards temperature and humidity. Thesupplying of air of a constant, predetermined temperature and humidityto the blower heads greatly facilitates and improves the tempering oithe glass and makes it easier to establish and maintain predeterminedcooling conditions.

Other objects and advantages of the invention will become more apparentduring the course of the following description, when taken in con- Same:

ing is adapted for the tempering of glass sheets or plates, it will beunderstood that the invention being treated in any way, passed directlyto the is in no way limited to the tempering of fiat sheets rarity ernipples it the drawing, the means for heating the glass sheets comprisesa furnace designated in its entlrety by the letter A, while the meansfor subsequently chilling or cooling the' sheets isv desig natedgenerally by the letter B. The cooling means B is arranged directlyabove the' furnace A so that the glass sheet 5, after being heated groseobtained by conditioning the en before it within the furnace, can betransferred directly to Y the cooling means without any undue loss ofheat and without being yadversely affected by atmospheric conditionsduring the transfer. The glass sheet 5 is suspended in a-vertica1position during the h'eating and cooling operations by relatively smalltongs 6 engaging the sheet'near its upper edge and being carried by asuitable supporting means 'I'he furnace A may be of an electricallyheated type and is provided with a top opening 8 through which the glasssheet Beto be treated may be inserted and removed. Any suitableremovablev covering can be used for th`e opening 8 as will be apparent.For the purposeof heating the furnace, electrical heating elements s maybe used in commotion with baille plates I which deiine therebetween vachamber for receiving the glass sheet 5. By means of any conventionalindicating `and control mechanism th'e temperature of the furnace can`be regulated to heat the glass sheet to approximately its point ofsoftening, which is in the neighborhood of-.1250 degrees Fahrenheit forordinary fiat glass,

Wh'en the glass sheet has been heated to the desired temperature withinthe furnace, it is lifted therefrom through the top opening l and ingmeans B; said i means comprising spaced blower heads II and I2 connectedby conduits I 3 and I4 respectively to suitable blowing apparatus, whichwill be hereinafter described, so th'at jets or blasts of air can bedirected simultaneously upon opposite surfaces of the glass sheet whenlbrought into position between said blower heads.

Each blowerI head may be provided `with a pluf As shown in Flg.v2, theconduits I3 and I4 associated with the blower heads l I and I 2 areconnected at their opposite ends to a common air supply pipe VI6 havinginterposed therein a blower 'Il operable from a motor I8. Upon operationofl the blower, air will be drawn 'into the outer open end of pipe I8and forced through the conduits I 3 and I4 to yblower heads II and I2 lwhere it-will be discharged through the nipples I against the glasssheet 5. Y

As pointed out above, it h'as beenheretofore customary to take the airfor cooling directly from the atmosphere and deliver it to the blowerheads without lin any way treating or conditioning the same. Also, thatwith such method it is diilicult to maintain established `predeterminedcooling conditions over any considerable periodA of time because ofvariations in th'etemperature and humidity of the air. In accordancewith this invention, the above objections are avoided and a morepositive control ofthe` cooling of the is supplied to the blower heads.The result is that the cooling air has a constant, predeterminedtemperature and moisture content.

`To this end, there is also interposed in the air supply pipe I 8 a heatexchanger I9 of any suitable constructlon and also a dehumidifier 20 ofany preferred type. For example, fthe dehumidiiler may be of the generaltypedisclosedfin the Sweets Catalog File (process industries) forsl942,at 5c/2; while a heat exchanger such as-isshowne A at 1e/5 in the samecatalog ille can be used.v Withi.- i I this arrangement, the air drawnthrough the pipeaV I6 by the blower I1 is caused to pass rst through thedehumidifier and then through lthe heat exchanger before reaching saidblower. During its passage through the dehumidifier 20 lthe airistreated so that it will have a predetermined moisture content and uponpassing through the heat is further treated so that it f j is of apredetermined temperature. Thus, ren the temperature and exchanger I9the air garclless of variations in humidity of the atmosphere, thetemperature and moisture content of the to the blower heads will remainconstant so. that a more uniform product is obtainable, i. efglasssubjected immediately to the action of the cool? vention herewith shownsheets or other glass articles having strain therein at selected pointsand s, desired predetermined breaking pattern. l

Although improved results can be obtained over `the usual method ofmaintaining the cooling air o at a constant, predetermined temperature,even though the moisture content thereof may vary somewhat, it ispreferred for best results that both the temperature and humidity of thecooling air be prevented from fluctuating.

It is to be understood that the form of the inand described is to betaken as the preferred embodiment of the same.

40 and that various changes in the shape, size and arrangement of partsmay be resorted to without departing from the spirit of the invention orthe through' which the Jets or blasts of air are directed against thesheet.

scope of the subjoined claims.

I claim-z VAl. In a method of tempering glass sheets or other glassarticles wherein said sheetsvor articles are rst heated to a temperatureapproximating the softening point of the glass and then suddenly cooledby being subjected to the direct action of air under pressure, the stepsof conditioning air by removing moisture therefrom to bring said air toa predetermined humidity and bringing the air to a predeterminedtemperature, and then directing thev conditioned air upon successiveheated glass sheets or other glass articles.

2. In the method of tempering glass sheets or other glass articleswherein said sheets or articles are first heated to a temperatureapproximating the softening point of the glass and then suddenly cooledby being subjected to the direct action of air under pressure, the stepscomprising conditioning air received directly from the atmosphere bydehumidifying said air to a predetermined humidity, then bringing thedehumidified air to a predetermined temperature, andthen blowing theconditioned air upon successive glass sheets or other glass articles.

, GERALD WHITE.

cooling .airdelivered

